Inspection and Testing Question please -NO MAIN EARTH??

Postby Sparkydelux » Thu Oct 01, 2009 1:31 pm

Hi Guys,

I'm a little stumped on a house I just tested.
Did all my relevent tests, all went well until I decided to do my Ze test.

Disconnected the main earth from the board to test and it came up as 153Ω!!!!
The system is a TN-S system and there are about 3 little pieces of steel wire twisted together going into an earth clamp. Even when i touched the earth clamp it was loose.

When I did the Zs it came up as 3.12Ω but that is with all the bonding attached to it. And I assume it was geting some form of earth off the pipework running in the ground. (just an assumption)

I have never encountered a problem like this. I though it was my tester and even used a different one.

I have done some testing but when things like this crop up I become foggy.

What should I do? I need to do something!notify the client about this and possibly the Authority (if it has lost its earth along the way)?

So far the rest of the circuits are all good with a few items that require upgrading for 17th edition but this earth has me stumped. I cannot issue her the report until I know whats wrong, hence my question.

I look forward to people's input and remarks / guidence.

Kind Regards,

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Simply Build It

Postby sparx » Fri Oct 02, 2009 8:16 pm

Hi, you mention TN-S so was the main earth on the supply cable metal outer sheath, & is this the clamp you refer to?

3 pieces of wire? it should be a 16mm2 between board and M.E.Terminal.
More Info Please, I'm curious
BTW when I do an inspection/test I always fill in on front sheet first:
Ze/PFC main earth size, main bonding size and confirm connected otherwise all other readings are meaningless and a waste of time as you are about to have to redo all IR's (which should be done with CPC's connected to earth bar), all Zs's will change after fixing faulty main bond.

Is this in town/city or country area? if there are overhead lines around I have found underground service to house with earth on cable sheath, but other end went up pole and L&N connected but sheath turned back and not connected!

First thing is to confirm TN-S system, make sure continuity of main earth between board and intake position, is it same looking cable each end or has there been a joint, it should be easy since only allowed 3 metres long!
Once happy with this then it is the owners responsibility to contact REC about condition of their connection to their cable, which they are not obliged to provide, you may end up having to request TN-C-S or go T.T.

Presume you are doing PIR, if so you need to stop now and get the fault fixed first, this should have been covered when you did your 2391-10 inspection & test course.
Ensure you have 'Professional Indemnity' cover with your P.L. insurence if doing I&T's, as you are giving a professional opinion as to the safe condition of the property!
regards SPARX
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Postby Sparkydelux » Mon Oct 05, 2009 1:26 pm

Hi Sparx,

The system apprear to be a TN-S.

The clamp is on the outer sheath connected to 3 'shreds'(shreds as in steel wire the diameter if 1.5mm cable) of cable appearing to go back into the sheath cover.

The main earth cable is 16mm and goes from the clamp to an earth Junction. Then the Earth cable goes from the Junction to the MET on the DB. --------At the junction is where the main equipotential bonding comes off too. This is in 10mm.

There are no additional joints in the cable besides the ones at the Junction. These were secure anyway when I checked.

I realise that I made a ROOKIE mistake by not completing the Ze and PFC first as the system was already live and working. i did the stupid thing of assuming it was all ok. A hard lesson learnt.

There are no overhead feeds besides telephone lines.
Feed into house comes via underground.

The remainder of the ciruits have CPC's and R1+R2 values were given. I had to do bonding as there was only a few items of Equiptential bonding done and the system has no RCD protection. This I guess is useless if there is no Main earth.

How does something like this get overlooked or is it just complacency?

I am in the process of getting affiliated and was going to use this as one of my criteria's I needed to fulfill. I used to live here and offered a Pro Bono service for the chance to get the affilitation done.

I see your caption about PL and Professional Indemnity, well, to be honest, this is something I need to still cover myself with as I am not at that stage yet. i hope you can shine some more light on what i'd need to do to set up. I take it you operate for yourself?

I look forward to your valuable response and guidence.

Kindest Regards,

Posts: 42
Joined: Tue Jul 03, 2007 9:32 pm

Postby super sparks » Tue Oct 06, 2009 4:30 pm

My personal recomendations would be as follows;

Firstly, disconnet the Main Earth (obviously ensure the fuse board is isolated), attach a new clamp ensuring all surfaces are clean from rust etc, Test Ze, if youre still getting a bad result, I would think about an earth electrode ( I assume there is a RCD, if not, one will need to be installed), if the result is ok, then replace the earth cable to the board and test again.
There are several reasons why the Ze could be high, but at the end of the day, you have to lower it otherwise your results will not be acceptable and you will not be able to issue a certificate (breaking capacity of breakers is one I often forget).
I also have had experiance of TT systems where it dives underground, so I would recomend another good look around.
super sparks
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Postby sparx » Wed Oct 07, 2009 3:18 pm

Hi again S-d-Lux.
I misunderstood part of your original post regards the 3 strands, i assume now that they are coming from REC's cable.
It should give good reading even with so few strands so can only believe some how other end not connected.
I see your thinking re having something to show, so it is a bit of a loser for you!
Two exits for you, either fit RCD plus rod as suggested by S-S or apply for PME, TN-C-S connection which can take ages.
Any changes done though will not come up to 17th standard so will entail a code 4, not what you want!
First option will make place safer but you will need to rethink strategy on using job for application to scheme which is what i think was your intention , [unless of course A N Other had previously fitted the rod & RCD and your inspection shows a TT system in place already....]
I didn't say that!!
What a quandry we find ourselves in by trying to do things right,
best wishes SPARX
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Postby Sparkydelux » Thu Oct 08, 2009 8:22 am

Hi Guys,
Thanks for the replies.
There definitely is no earth rod and there is no RCD protection. And NO Earth.
Can you see my dilemma?
Basically this is a waiting time bomb for someone. I am ashamed to say this, but I wish I hadn't even opened my mouth. But in the same instance I don't want to do an OSTRICH and bury my head in the sand. This is a good learning curve for me and I want to accomplish it.

Back to the dilemma, I could fit an earth rod as the main intake runs inside of an external wall. But it's going to look a little suspicious having a TT system in the suburbs! If its the way forward then I'd recommend it.

I dont have much area to run the earth into as it only has a small path way to run into. Never the less, it'll provide an earth, which they don't have already.

Secondly they'll require a board change as theirs is still operating on 30A Breakers, so that'll require upgrading.

As all this is good and essential protocol, I can only suggest it as a recommendation. I am not sure what their funds are like.

I assume (if they agree to go ahead with the works) I'd have to re-test all my Zs /PFC /Ze and newly added RCD trips. R1+R2 wont be effected as is IR values.

Should be a doddle. Board change, earth rod and a bit of testing.

Where do I stand if they decline the works? As a duty holder, what should I do from there on?

I also want to issue a PIR and obsevation list to them. Ideally I cant issue a Schedule of test results as the items are unsatisfactory and all readings will be totally inaccurate once the new earth is installed.

Can the PIR / Observations documents still be issued as a recommendation or should I just give them something on a letter head rather than a formal document?

I thank you guys for you input,


Sparkydelux (S-D-Lux)
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Joined: Tue Jul 03, 2007 9:32 pm

Postby sparx » Sat Oct 10, 2009 9:37 pm

Hi again, leaving aside your reason for doing the PIReport,
It's a report like the MOT on your car, if it fails the garage doesn't fix it, they just give the ticket with list of problems.
They won't like report with problems -no one does- but you may just save a life! It's that simple, do any relevent tests, mark what fails ie main earth, As it's major I would add an explaination as to meaning of a
Code [1] if not already on report sheets and give them the options IN WRITING and keep a copy, bow out the door - flanged!!
If they don't want to pay to get it made safe you can do no more,
regards SPARX
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Joined: Wed Mar 21, 2007 8:33 pm
Location: The fifth continent.

Postby Sparkydelux » Sun Oct 11, 2009 10:54 am

Thanks for the advice guys.

Much appreciated.
Posts: 42
Joined: Tue Jul 03, 2007 9:32 pm

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